Pharmacokinetic equivalence of CT‐P39 and reference omalizumab in healthy individuals: A randomised, double‐blind, parallel‐group, Phase 1 trial

Abstract Background CT‐P39 is being developed as a biosimilar of reference omalizumab. This study aimed to assess the pharmacokinetic equivalence of CT‐P39 to European Union‐approved and United States‐licensed reference omalizumab (EU‐ and US‐omalizumab, respectively). Methods This two‐part, randomised, parallel‐group, double‐blind Phase 1 trial (NCT04018313) was conducted in healthy individuals with a total immunoglobulin E (IgE) level ≤100 international units (IU)/ml at screening. In part 2, described herein, participants were randomised (1:1:1) to receive a single 150 mg subcutaneous dose of CT‐P39, EU‐omalizumab, or US‐omalizumab. The primary endpoint was pharmacokinetic equivalence in terms of area under the concentration–time curve (AUC) from time zero to the last quantifiable concentration (AUC0–last), AUC from time zero to infinity (AUC0‐inf), and maximum serum concentration (C max). Equivalence was concluded if 90% confidence intervals (CIs) of the geometric least‐squares means ratios were contained within the predefined 80%–125% equivalence margin. Additional pharmacokinetic parameters, pharmacodynamics, safety, and immunogenicity were also evaluated. Results Overall, 146 participants were randomised (CT‐P39, N = 47; EU‐omalizumab, N = 49; US‐omalizumab, N = 50). For all primary pharmacokinetic parameters, 90% CIs for pairwise treatment comparisons were within the 80%–125% equivalence margin, demonstrating pharmacokinetic equivalence. Decreases in free IgE and increases in total IgE serum concentrations were comparable across groups. CT‐P39 was well tolerated. Safety endpoints were comparable across groups: there were no treatment‐related serious adverse events, deaths, or discontinuations due to treatment‐emergent adverse events. Conclusions CT‐P39 was well tolerated and demonstrated pharmacokinetic equivalence with EU‐omalizumab and US‐omalizumab following administration of a single dose in healthy individuals.


| INTRODUCTION
Omalizumab is a humanised monoclonal antibody targeting immunoglobulin E (IgE). 1  been received for indications comprising asthma in adults and paediatric patients aged ≥6 years, nasal polyps in adults, and chronic spontaneous urticaria in adults and adolescents aged ≥12 years 3 ; EC approval has been received for allergic asthma in patients aged ≥6 years, chronic rhinosinusitis with nasal polyps in adults, and chronic spontaneous urticaria in adults and adolescents aged ≥12 years. 2 Accordingly, global, European, and US treatment guidelines recommend the use of omalizumab in selected patients as an add-on therapy for uncontrolled moderate or severe asthma, [4][5][6][7] which may include allergic and non-allergic eosinophilic asthma, 5 in the treatment of nasal polyps, 8 and as add-on therapy for chronic urticaria refractory to a high-dose, second-generation H 1 -antihistamine. [9][10][11] The cost of biologic therapies used to treat allergic diseases is high, which can limit patient access to these treatments. [12][13][14][15] Biosimilars can offer cost savings, potentially allowing more patients globally to benefit from biologic therapy, 14,15 and the future potential role of biosimilars of reference omalizumab has been mentioned in British treatment guidelines. 11 Biosimilars are assessed via dedicated FDA and European Medicines Agency pathways, and regulatory approval requires demonstration that there are no clinically meaningful differences in terms of safety, quality, and efficacy between the candidate biosimilar and original biologic/reference product. 16,17 Ultimately, regulatory approval is based on the totality of evidence gathered through a stepwise comparability exercise involving analytical, non-clinical, and clinical studies, which together evaluate pharmacokinetics (PK), efficacy, safety, immunogenicity, and potentially pharmacodynamics (PD), of the candidate biosimilar. [16][17][18] No biosimilars of reference omalizumab have yet obtained regulatory approval from the FDA or EC. 19,20 However, CT-P39 is in development as a reference omalizumab biosimilar, and as part of the development programme, a two-part Phase 1, single-dose, double-blind, parallel-group, randomised study was conducted. Part 1 was a first-in-human study to evaluate the initial safety of CT-P39 versus European Union-approved reference omalizumab (EU-omalizumab): no safety issues were identified and CT-P39 was well tolerated (unpublished data on file). Part 2, described in this article, aimed to demonstrate the PK equivalence of CT-P39 to EU-omalizumab and United States-licensed reference omalizumab (US-omalizumab), all administered via prefilled syringe (PFS). PD, safety, and immunogenicity were also evaluated. Two comparators were used to satisfy US and EU regulatory requirements to demonstrate similarity to a reference product marketed in the respective regions.

| Study design
This was a two-part, randomised, parallel-group, double-blind, Phase

| Study endpoints
The primary objective (which was assessed in part 2 of the study) was to evaluate the PK equivalence of CT-P39 to EU-omalizumab and US-omalizumab, assessed in terms of area under the concentrationtime curve from time zero to the last quantifiable concentration (AUC 0-last ), area under the concentration-time curve from time zero to infinity (AUC 0-inf ), and maximum serum concentration (C max ).
Additional PK parameters were evaluated as secondary endpoints, including the time to maximum serum concentration (T max ), terminal half-life (t 1/2 ), terminal elimination rate constant (λ z ), apparent total body clearance (CL/F), apparent volume of distribution during the terminal phase (V z /F), and percentage of the AUC 0-inf obtained by extrapolation (%AUC ext ). Secondary PD endpoints assessed for free IgE comprised the minimum serum concentration (C min ), time to minimum serum concentration (T min ), and maximum percentage decrease from baseline; for total IgE, they comprised C max , T max , and maximum percentage increase from baseline. Safety and immunogenicity were assessed throughout the study.

| Study assessments
Blood samples for PK and PD assessments were collected at screening (Day −28 to Day −2; for PD assessment of total IgE only), pre-dose on Day 1, at 6, 12, 24, 48, and 72 h after the start of study drug administration, and on Days 6,8,11,15,22,29,43, 57, 71, 85, 106, and 127. Validated electrochemiluminescence methods were used to measure total serum omalizumab levels and serum free IgE levels; total IgE (i.e. free and omalizumab-bound IgE) was measured using ImmunoCAP™ Total IgE (ThermoFisher Scientific). PK parameters were calculated based on measured total serum omalizumab concentrations by non-compartmental methods, using Phoenix

| Statistical analysis
Log-transformed primary endpoints were analysed by analysis of covariance at an alpha level of 0.05. Treatment was a fixed effect and the stratification criteria for randomisation were covariates.
In part 2, a sample size of 42 in each group was required to provide 90% statistical power to demonstrate PK equivalence, based on the equivalence margin, two one-sided tests, each with an alpha level of 0.05, a 30% coefficient of variation, and an expected ratio of 1.03.

| PK results
Equivalence was demonstrated between CT-P39, EU-omalizumab, and US-omalizumab in terms of the log-transformed primary PK endpoints AUC 0-last , AUC 0-inf , and C max ( Table 2). The 90% CIs for the ratios of gLSMs were within the predefined 80%-125% equivalence margin for each pairwise treatment comparison. Primary and secondary PK parameters were generally similar between treatment groups (Table 3), and, following a single administration of study drug, serum omalizumab concentrations were comparable between groups up to Day 127 ( Figure 1A).

| PD results
Mean serum concentrations of free IgE rapidly decreased following study drug administration, to a comparable degree for each of the three treatment groups ( Figure 1B

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comparable levels between treatment groups, and decreased towards baseline at the end of the study ( Figure 1C).
PD parameters for free and total IgE were generally comparable between treatment groups (Table 4). Although there were some numerical differences in maximum percentage increase in total IgE, these were likely accounted for by the high inter-participant variability. There was one notable outlier in the US-omalizumab group, with a maximum increase exceeding 10,000% (data not shown).

| Safety
All participants successfully received a single dose of study drug.
There were no TEAEs leading to study discontinuation or death.
The most frequently reported manifestation of ISR was injection-site erythema reported in 5 (10.6%), 3 (6.1%), and 3 (6.0%) of participants in the CT-P39, EU-omalizumab, and US-omalizumab groups, respectively. All ISRs were grade 1 in intensity and all participants recovered from the event.
Overall, there were no notable differences between treatment groups in terms of clinical laboratory findings, and no notable safety findings in terms of vital signs, physical findings, or other observations. Immunogenicity was lower in the CT-P39 group than in the reference omalizumab groups. After study drug administration, 1 (2.1%), 13 (26.5%), and 18 (36.0%) participants in the CT-P39, EU-omalizumab, and US-omalizumab groups, respectively, had at least one positive ADA result. At least one positive NAb result was reported in 1 (2.0%) and 3 (6.0%) participants in the EU-omalizumab and US-omalizumab groups, respectively. No participants in the CT-P39 group had detectable positive NAb titres.

| DISCUSSION
Mean peak exposure and total exposure are key parameters for the demonstration of PK similarity of a candidate biosimilar to its reference product during a biosimilar clinical development programme. 16,17,21 The present study showed that single doses of CT-P39, EU-omalizumab, and US-omalizumab were equivalent in terms of PK, according to predefined equivalence criteria. In this study, the 90% CIs for each primary PK endpoint were contained entirely within the predefined 80%-125% equivalence margin.
Therefore, equivalence was demonstrated between CT-P39, EU-omalizumab, and US-omalizumab in terms of PK. After study drug administration, free IgE decreased while total IgE increased. PD results for free IgE were comparable between groups in terms of C min , T min , and maximum percentage decrease. Increases in total IgE level were comparable between groups, although numerical differences were noted for the maximum percentage increase in total IgE. This was likely driven by inter-participant variation and/or aberrant values, with one notable outlier observed in the US-omalizumab group. The value was greatly divergent from that for other participants, but no clear factor that could account for the difference was identified. Secondary PK parameters and safety findings were generally comparable between treatment groups.
In the current study, the PK parameters observed across groups were broadly similar to those previously noted in a study evaluating reference omalizumab in adults with stable atopic disease. 22 Importantly, reference omalizumab and/or free IgE concentrations have been demonstrated to correlate with clinical outcomes in populations of patients with asthma or urticaria, [23][24][25] underlining the importance of assessing these measures when  PD parameters were not calculated for participants with free IgE concentrations below the lower limit of quantification at baseline. Maximum % decrease and maximum % increase were not calculated for participants with a free IgE concentration above the upper limit of quantification at baseline or a total IgE concentration below the lower limit of quantification at baseline, respectively.  Overall, the safety profile of CT-P39 was comparable to those of EU-omalizumab and US-omalizumab. In this study, the most frequently reported TEAE was headache. This is broadly aligned with the 'common' incidence of headache described in the EU prescribing information for reference omalizumab, which is based on clinical studies in patients with allergic asthma, chronic rhinosinusitis with nasal polyps, and chronic spontaneous urticaria. 2 Headache was also the most common TEAE reported during a study of reference omalizumab administered to adult patients with stable atopic disease. 22 Importantly, there were no TEAEs leading to study discontinuation or death, and only one TESAE occurred (head injury caused by assault), which was not treatment related. Furthermore, of the AESIs evaluated in the study, only ISRs were observed and the frequency of these events was in keeping with the 'common' incidence reported in the EU prescribing information for reference omalizumab. 2 Notably, lower immunogenicity was observed in the CT-P39 group than in the two reference omalizumab groups. However, these results should be interpreted with caution as the sample size was relatively small. In addition, no participant experienced an increase in ADA titre after treatment and the majority of ADA-positive participants had a transiently low ADA titre of 1 in 25, the minimum required dilution of the assay. Relatively high immunogenicity was reported for reference omalizumab in this study compared with that in previous studies in patients with allergic disease, 3,26 possibly due to the use of a more sensitive and drug-tolerant ADA assay technology. ADA detection is highly dependent on assay sensitivity and specificity, making comparisons between studies difficult. 3 Nevertheless, NAb detection was low across groups in this study.
A limitation of the present study is that most (>75%) participants in each group were White, potentially limiting generalisability to other racial or ethnic groups. However, previous research with reference omalizumab has not found any clinically meaningful differences in PK and PD based on race, and efficacy and safety profiles do not differ by race or ethnicity. 25,[27][28][29] Building on the findings of the present study, the double-blind, randomised, parallel-group, Phase 3 CT-P39 3.1 study (NCT04426890) is ongoing and aims to demonstrate equivalence of the clinical efficacy, PK, PD, and safety of CT-P39 versus EU-omalizumab in patients with chronic spontaneous urticaria. 30 The primary endpoint of the study will assess therapeutic similarity between CT-P39 and EU-omalizumab. 30 In conclusion, this study demonstrated PK equivalence of CT-P39 to EU-omalizumab and US-omalizumab following administration of a single dose in healthy individuals. As part of a stepwise biosimilar development programme, this study provides PK evidence of high similarity for CT-P39 and reference omalizumab. A single dose of CT-P39 was found to be safe and well tolerated.

AUTHOR CONTRIBUTIONS
All authors have made substantial contributions to the conception and design of the study or the acquisition, analysis, or interpretation of data; drafted the manuscript or revised it critically for important intellectual content; given final approval of the version to be published; and agreed to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.